[Mesa-dev] [PATCH] list: add some iterator debug

[Ilia Mirkin]

Why not just do it in a way that works for everyone? Both the do/while
method and the ifdef-based method that I suggested work everywhere. Or
is there another reason you prefer to use those statement expressions?

On Sat, May 25, 2019 at 6:21 PM Rob Clark <robdclark at gmail.com> wrote:
>
> Is there a convenient #ifdef I can use to guard the list_assert()
> macro..  I don't really mind if MSVC can't have this, but would rather
> not let it prevent the rest of us from having nice things
>
> BR,
> -R
>
> On Sat, May 25, 2019 at 1:23 PM Jason Ekstrand <jason at jlekstrand.net> wrote:
> >
> > Yeah, that's a GNU extension. It also works in clang but not MSVC which is
> > used to build NIR.
> >
> > On May 25, 2019 13:30:29 Rob Clark <robdclark at gmail.com> wrote:
> >
> > > On Sat, May 25, 2019 at 11:13 AM Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> > >>
> > >> On Sat, May 25, 2019 at 2:03 PM Rob Clark <robdclark at gmail.com> wrote:
> > >> >
> > >> > From: Rob Clark <robdclark at chromium.org>
> > >> >
> > >> > Debugging use of unsafe iterators when you should have used the _safe
> > >> > version sucks.  Add some DEBUG build support to catch and assert if
> > >> > someone does that.
> > >> >
> > >> > I didn't update the UPPERCASE verions of the iterators.  They should
> > >> > probably be deprecated/removed.
> > >> >
> > >> > Signed-off-by: Rob Clark <robdclark at chromium.org>
> > >> > ---
> > >> >  src/util/list.h | 23 ++++++++++++++++++-----
> > >> >  1 file changed, 18 insertions(+), 5 deletions(-)
> > >> >
> > >> > diff --git a/src/util/list.h b/src/util/list.h
> > >> > index 09d1b4cae64..6d89a42b226 100644
> > >> > --- a/src/util/list.h
> > >> > +++ b/src/util/list.h
> > >> > @@ -43,6 +43,13 @@
> > >> >  #include <assert.h>
> > >> >  #include "c99_compat.h"
> > >> >
> > >> > +#ifdef DEBUG
> > >> > +#  define LIST_DEBUG 1
> > >> > +#else
> > >> > +#  define LIST_DEBUG 0
> > >> > +#endif
> > >> > +
> > >> > +#define list_assert(cond, msg)  ({ if (LIST_DEBUG) assert((cond) && msg); })
> > >>
> > >> Not sure if it's worth worrying about, but this style of macro
> > >> definition can be dangerous. One might use it as
> > >>
> > >> if (x) list_assert()
> > >> else blah;
> > >>
> > >> With the macro defined as-is, the "else blah" will get attached to the
> > >> if in the macro. I believe the common style is to do do {}while(0) to
> > >> avoid such issues (or to use an inline function). Alternatively, just
> > >> define it differently for LIST_DEBUG vs not.
> > >>
> > >
> > > I think the ({ ... }) should save the day..
> > >
> > > (hmm, is that c99 or a gnu thing?  I've it isn't avail on some
> > > compilers I guess we should disable list_assert() for those?)
> > >
> > > BR,
> > > -R
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> >
> >
> >